Fenn traps are widely used in New Zealand for control of small predators. Introduced stoats (Mustela erminea) pose a significant risk to many indigenous New Zealand bird species, and the Department of Conservation (DOC) has used Fenn traps to reduce their numbers over the last
20–30 years. Changes to New Zealand animal welfare legislation in 1999 focused attention on whether this trap killed quickly and consistently and, therefore, pen tests were carried out to assess their killing performance. A guideline for testing traps was developed for the National Animal
Welfare Advisory Committee, and to meet the guidelines kill traps must render all ten test animals irreversibly unconscious within three minutes. Testing is stopped as soon as three animals fail the criterion. New Mk IV and MkVI and used MkVI Fenn traps were tested. With the exception of one
stoat captured in a new MkVI trap, all stoats remained conscious until euthanased at 5 minutes, and consequently only three stoats were used in each test. In response to these results, a new series of traps was developed (DOC 150, 200, and 250). These killed all 10 test animals, with all rendered
irreversibly unconscious within 3 minutes and most unconscious in less than 20 seconds. The new DOC traps have also been tested for their efficacy at killing other small mammals including rats, ferrets, and hedgehogs, which are often captured as non-target species. As these new traps replace
Fenn traps in Department of Conservation stoat control operations, significant improvements in the welfare of trapped stoats should result.